In the preparation of synthetic resinous products, it is often desirable to have an apparatus for evaluating the impact resistance of a synthetic resinous product which corresponds closely to practical toughness of the synthetic resinous product in end-use applications.
Experience has indicated the advisability of modifying or creating new testing apparatus to ensure reproducible, meaningful results. Previous evaluation methods have ranged from error-prone, subjective tests, such as striking vacuum cleaner suction heads (formed from synthetic resinous materials) against rigid walls and throwing toys (formed from synthetic resinous materials) down a flight of stairs, to the more objective tests, such as the notched Izod impact test wherein a large swinging pendulum strikes a test specimen into which notches have been machined, the measure of impact resistance being the distance which the pendulum travels after breaking the test specimen.
U.S. Pat. No. 2,892,342 discloses a testing apparatus which is used to determine the fatigue and impact strength of plastic materials whereby a weighted hemispherical shape is repeatedly raised and dropped against a test piece until sample failure occurs.
Experience has demonstrated that the practical impact performance of formed synthetic resinous products does not necessarily depend upon the Izod impact test value for the particular resin. Rather, the practical impact performance depends upon a combination of a number of other properties such as tensile rupture, percent elongation, percent gel, or swell index of the rubber phase.
It would be desirable if there were available an improved apparatus for the testing of synthetic resinous products.
It would also be desirable if such an apparatus yielded reproducible results.
It would be desirable if the impact portion of the apparatus had a reduced tendency to rebound from the surface of the test piece upon impact.
It would further be desirable if such an apparatus were inexpensive.